Prep the pan and oven: Heat oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment, leaving overhang for easy lifting. Lightly grease the sides.

Make the crust: In a bowl, mix 2 cups almond flour, 4 tablespoons granulated sweetener, a pinch of salt, and 6 tablespoons melted butter until it looks like damp sand. Press evenly into the pan. Prick a few holes with a fork.

Par-bake the crust: Bake 10–12 minutes until lightly golden at the edges. Set aside to cool for 5 minutes.

Blend the filling: In a blender or food processor, add 2 cups cottage cheese, 2 large eggs, 1/3–1/2 cup granulated sweetener (to taste), 1 teaspoon vanilla, 1 teaspoon lemon zest, 1 tablespoon cornstarch or arrowroot, and a pinch of salt. Blend until completely smooth and creamy, about 30–45 seconds. Scrape sides and blend again if needed.

Fold in berries: Pour the filling into a bowl and gently fold in 1 cup blueberries. If using frozen berries, dust lightly with a teaspoon of almond flour first to reduce bleeding.

Assemble: Pour the filling over the warm crust. Smooth the top. If you like, sprinkle a pinch of cinnamon over the surface.

Bake: Return to the oven and bake 28–35 minutes, until the center is mostly set with a slight jiggle and the edges look puffed. If the top browns too fast, tent loosely with foil.

Cool completely: Place the pan on a rack and cool to room temperature, about 1 hour. Then chill at least 2 hours to set for clean slices.

Slice and serve: Use the parchment to lift out. Cut into 12 bars. Serve chilled or at cool room temperature.